Hot water supply device

ABSTRACT

A hot water supply device includes: a first pipe connected to a water inlet; a flow detector detecting a flow of water in the first pipe; a heating mechanism heating the water; a second pipe through which warm water flows, connected to the first pipe via a third pipe; a circulating pump disposed in a path of the first pipe, sending the warm water in the third pipe toward the heating mechanism during operation; and a control device. Based on acceptance of an execution command of an instant hot water circulation mode, the control device operates the circulating pump, and, in response to a set hot water output temperature exceeding a limit temperature, adjusts a heating temperature of the heating mechanism, so that the temperature of the warm water becomes equal to or lower than the limit temperature.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority benefit of Japan Application No. 2019-213295, filed on Nov. 26, 2019. The entirety of the above-mentioned patent application is hereby incorporated by reference herein and made a part of this specification.

BACKGROUND Technical Field

The disclosure relates to a hot water supply device, and more specifically, to a safety function of an instant hot water circulation mode.

Related Art

Some hot water supply devices have a so-called instant hot water function of supplying warm water of an appropriate temperature immediately after the start of hot water supply even if the hot water supply devices have not been used for a long time. A hot water supply device generally includes an inflow side pipe, an outflow side pipe, and a heating mechanism.

In the hot water supply device having an instant hot water function, warm water is circulated through the pipes and the heating mechanism in the hot water supply device by a circulating pump (hereinafter referred to as an “instant hot water circulation mode”). By circulating the warm water inside the device itself, the hot water supply device makes it possible to supply warm water of an appropriate temperature immediately after the start of hot water supply.

Depending on the country or region, a pipe connected to a warm water faucet and a pipe connected to a cold water faucet may be connected by a circulation pipe. In the hot water supply device connected to the water pipes of this configuration, in the instant hot water circulation mode, the warm water circulates through the heating mechanism and the circulation pipe. Hence, when the warm water is circulating at a high temperature, there is a possibility that the high-temperature warm water may flow out when a user turns on the cold water faucet, which is dangerous. Hence, there is a need for a technique for enhancing safety in the instant hot water circulation mode.

Regarding instant hot water circulation, for example, Japanese Patent Laid-Open No. 2007-003165 (Patent Document 1) discloses an instant hot water unit in which “a temperature detector is provided between an electric heater of a return pipe and a second connection part on an upstream side of a hot water supply pipe, and a high-temperature hot water output prevention means, which stops operation of a circulating pump and the electric heater when a temperature detected by the temperature detector exceeds an upper limit temperature set higher than an instant hot water set temperature, is provided in a controller” (see the [Abstract]).

Another example relating to instant hot water circulation is disclosed in Japanese Patent Laid-Open No. H11-014142 (Patent Document 2).

Patent Documents

[Patent Document 1] Japanese Patent Laid-open No. 2007-003165

[Patent Document 2] Japanese Patent Laid-open No. H11-014142

According to the techniques disclosed in Patent Documents 1 and 2, in the case where the circulating pump has an ON failure (a state in which the circulating pump in operation cannot be stopped) in the instant hot water circulation mode, there is a possibility that high-temperature warm water may flow out from the cold water faucet. Therefore, there is a need for a technique for preventing outflow of high-temperature warm water from the cold water faucet even if the circulating pump has an ON failure in the instant hot water circulation mode.

One aspect of the disclosure provides a technique for preventing outflow of high-temperature warm water from a cold water faucet even if a circulating pump has an ON failure in the instant hot water circulation mode.

SUMMARY

A hot water supply device according to one embodiment includes: a first pipe connected to a water inlet; a flow detector detecting a flow of water in the first pipe; a heating mechanism heating the water flowing in from the first pipe; and a second pipe through which warm water heated by the heating mechanism flows. The second pipe is connected to the first pipe via an external third pipe. The hot water supply device further includes: a circulating pump disposed in a path of the first pipe, sending the warm water in the third pipe toward the heating mechanism during operation; and a control device controlling the circulating pump and the heating mechanism. Based on acceptance of an execution command of an instant hot water circulation mode, the control device operates the circulating pump, and, in response to a set hot water output temperature exceeding a predetermined limit temperature, adjusts a heating temperature of the heating mechanism, so that a temperature of the warm water in the instant hot water circulation mode becomes equal to or lower than the limit temperature.

According to one embodiment, even if the circulating pump has an ON failure in the instant hot water circulation mode, it is possible to prevent outflow of high-temperature warm water from a cold water faucet.

The above as well as other objects, features, aspects and advantages of the disclosure will become apparent from the following detailed description of the disclosure which is understood in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates one example of a hot water supply device 100 with a circulation port.

FIG. 2 illustrates one example of a hot water supply device 200 without a circulation port.

FIG. 3 illustrates one example of a configuration of a controller 250.

FIG. 4 illustrates one example of an outline of an operation of the hot water supply device 200 in a hot water supply mode.

FIG. 5 illustrates one example of an outline of an operation of the hot water supply device 200 in an instant hot water circulation mode.

FIG. 6 illustrates one example of an outline of an operation of the hot water supply device 200 in a case where a circulating pump 207 has an ON failure in the instant hot water circulation mode.

FIG. 7 illustrates an example of a first operation in the hot water supply device 200.

FIG. 8 illustrates an example of a second operation in the hot water supply device 200.

FIG. 9 illustrates another example of the hot water supply device 200 without a circulation port.

DESCRIPTION OF THE EMBODIMENTS

Embodiments of the technical idea according to the disclosure will be described below with reference to the drawings. In the following description, the same parts are denoted by the same reference numerals, and also have the same names and functions. Accordingly, detailed description thereof will not be repeated. In the following description, the entry of water or warm water into something is called “inflow.” The exit of water or warm water from something is called “outflow.”

A hot water supply device usually includes a port for inflow of tap water and a port for outflow of heated warm water. In addition, in some hot water supply devices, in order to circulate the warm water in the hot water supply devices, a circulation port is provided to allow the warm water that has flowed out from the port for outflow of heated warm water to flow into the hot water supply devices. Some hot water supply devices do not include an independent circulation port, and the port for inflow of tap water also serves as the circulation port.

Control in an instant hot water circulation mode according to the present embodiment can be suitably applied mainly to a hot water supply device without an independent port. First of all, a configuration of a hot water supply device with a port, a configuration of a hot water supply device without a port, and a configuration of a controller controlling a hot water supply device are described in order. Next, a method for controlling the hot water supply device according to the present embodiment will be described.

[Configuration of Hot Water Supply Device]

FIG. 1 illustrates one example of the hot water supply device 100 with a circulation port. The hot water supply device 100 includes a bypass servo 101, flow detectors 102 and 108, temperature detectors 103 and 105, a heat exchanger 104, a water servo 106, a circulating pump 107, ports 111, 112 and 113, and a controller 150.

The port 111 is connected to a water pipe 110 that supplies water. The water is supplied from the water pipe 110 to the hot water supply device 100 via the port 111. The water flows into the hot water supply device 100 due to an inflow water pressure from the water pipe 110. Hence, when a pipe in the hot water supply device 100 is filled with water or warm water, the inflow of water from the water pipe 110 to the hot water supply device 100 is stopped. In addition, when a valve 130 is open, the water flowing in from the water pipe 110 flows out from a hot water faucet 140.

A part of the water that has flowed from the port 111 into the hot water supply device 100 passes through a path 155 and flows into the heat exchanger 104. In addition, a part of the water that has flowed from the port 111 into the hot water supply device 100 flows out from the port 113 via paths 160 and 165. The path 155 is a path from an exit of the bypass servo 101 to an entrance of the heat exchanger 104. The path 160 is a path from the exit of the bypass servo 101 to a junction with the path 165. The path 165 is a path from an exit of the heat exchanger 104 to the port 113.

The port 112 is connected to the same pipe as the port 113. In the instant hot water circulation mode, the warm water that has flowed out from the port 113 again flows into the hot water supply device 100 from the port 112 and circulates via the heat exchanger 104.

The port 113 is connected to a pipe connected to the hot water faucet 140. In a hot water supply mode, the warm water that has flowed out from the port 113 is supplied to the user from the hot water faucet 140. The hot water supply mode is an operation mode when the warm water heated by the heat exchanger 104 flows out from the hot water faucet 140 (when the user uses the warm water). In the instant hot water circulation mode, the warm water that has flowed out from the port 113 circulates through the hot water supply device 100 via the port 112.

The bypass servo 101 adjusts a ratio between the amount of water flowing into the path 155 and the amount of water flowing into the path 160. As one example, the bypass servo 101 may include a faucet by means of a stepping motor or the like, and the amount of water flowing into the path 160 may be adjusted by this faucet. The water flowing into the heat exchanger 104 via the path 155 is heated by the heat exchanger 104 and becomes warm water. The water flowing into the path 160 mixes with the warm water flowing out of the heat exchanger 104 in the path 165 and adjusts the temperature of the warm water.

The flow detector 102 detects the amount of water flowing through the path 155. In one aspect, the flow detector 102 may include a water wheel or the like therein, and may detect the amount of water according to a rotation amount of the water wheel or the like. In that case, the flow detector 102 outputs, to the controller 150, a signal generated based on the rotation amount of the water wheel or the like. The signal output to the controller 150 may be a digital signal or an analog signal. Based on the input signal, the controller 150 may estimate the amount of water flowing through the path 155 and determine whether water is flowing through the path 155.

The temperature detector 103 detects a temperature of the water that has passed through the flow detector 102. As shown in FIG. 1, the water flowing in from the water pipe 110 and the warm water that has passed through the path 170 by the circulating pump 107 flow into the flow detector 102. Hence, in the case where the hot water supply device 100 is operating in the instant hot water circulation mode, the temperature detector 103 detects a temperature of the warm water circulating through the paths 155, 165 and 170. In addition, in the case where the hot water supply device 100 is not operating in the instant hot water circulation mode, the temperature detector 103 detects a temperature of the water flowing from the water pipe 110 into the hot water supply device 100. In addition, the temperature detector 103 may detect a temperature of water or warm water in which the water flowing from the water pipe 110 into the hot water supply device 100 is mixed with the warm water circulating through the paths 155, 165 and 170.

In one aspect, the temperature detector 103 may be a thermistor. In that case, the temperature detector 103 outputs, to the controller 150, a signal generated based on the temperature of the water that has passed through the flow detector 102. The signal output to the controller 150 may be a digital signal or an analog signal. Based on the input signal, the controller 150 may detect the temperature of the water flowing through the path 155.

The heat exchanger 104 (heating mechanism) raises the temperature of the water flowing into the heat exchanger 104 by using heat generated by a combustion mechanism (not shown) or the like. In one aspect, the combustion mechanism may be composed of a burner that generates heat by combustion of gas or petroleum or the like. In another aspect, the heat exchanger 104 includes therein a pipe having high thermal conductivity. A plate for transferring heat may be disposed around the pipe. The combustion mechanism heats the pipe and the plate. The water is heated by passing through the pipe and becomes warm water. The warm water flows out from the path 165 toward the port 113.

The temperature detector 105 detects a temperature of the warm water flowing through the path 165. When a valve 120 is open, the warm water passing through the path 165 flows out from the hot water faucet 140. Hence, it can be said that the temperature detector 105 directly detects the temperature of the warm water used by the user. In one aspect, the temperature detector 105 may be a thermistor. In that case, the temperature detector 105 outputs, to the controller 150, a signal generated based on the temperature of the warm water flowing through the path 165. The signal output to the controller 150 may be a digital signal or an analog signal. Based on the input signal, the controller 150 may detect the temperature of the warm water flowing through the path 165.

The water servo 106 adjusts the amount of the warm water flowing out from the port 113. As one example, the water servo 106 may include a faucet by means of a stepping motor or the like, and the amount of the warm water flowing out from the port 113 may be adjusted by this faucet.

When the valve 120 is open, the warm water that has flowed out from the port 113 flows out from the hot water faucet 140. In the case where the valve 120 is closed and the hot water supply device 100 is operating in the instant hot water circulation mode, the warm water that has flowed out from the port 113 flows into the port 112.

The circulating pump 107 circulates the warm water that has flowed in from the port 112 in the heat exchanger 104. In one aspect, the circulating pump 107 may be a pump driven by a DC motor or the like. In that case, the DC motor of the circulating pump 107 may be controlled by the controller 150.

The flow detector 108 detects the amount of warm water flowing through the path 170. In one aspect, the flow detector 108 may include a water wheel or the like therein, and may detect the amount of water according to a rotation amount of the water wheel or the like. In that case, the flow detector 108 outputs, to the controller 150, a signal generated based on the rotation amount of the water wheel or the like. The signal output to the controller 150 may be a digital signal or an analog signal. Based on the input signal, the controller 150 may estimate the amount of warm water in the path 170 and determine whether warm water is flowing in the path 170.

The controller 150 controls the entire hot water supply device 100. Specifically, the controller 150 estimates the amount of water in each path by acquiring the signals output by the flow detectors 102 and 108, and estimates the temperature of the water or warm water flowing through each path by acquiring the signals output by the temperature detectors 103 and 105. Further, the controller 150 may adjust the flow and temperature of the water or warm water by controlling various actuators (such as the bypass servo 101, the water servo 106, the circulating pump 107 and the heat exchanger 104). In one aspect, the controller 150 may be provided inside or outside the hot water supply device 100.

Next, an outline of operations in the hot water supply mode and the instant hot water circulation mode in the hot water supply device 100 will be described. In addition, an operation of the hot water supply device 100 in the case where the circulating pump 107 fails while the hot water supply device 100 is operating in the instant hot water circulation mode will also be described.

In the hot water supply mode, the hot water supply device 100 heats the water flowing in from the water pipe 110 with the heat exchanger 104, and causes warm water to flow out from the port 113. In the case where the valve 120 is open, the warm water flowing out from the port 113 flows out from the hot water faucet 140. The circulating pump 107 has stopped during the hot water supply mode, and the warm water that has flowed out from the port 113 does not flow into the path 170 or only a small amount thereof flows into the path 170.

In the instant hot water circulation mode, the hot water supply device 100 heats the water flowing in from the water pipe 110 with the heat exchanger 104, and causes warm water to flow out from the port 113. The circulating pump 107 is operating during the instant hot water circulation mode, and pushes out the warm water that has flowed out from the port 113 toward the path 170. The warm water that has flowed out from the port 113 is pushed out by the circulating pump 107 and flows into the path 170 as long as the valve 120 is closed. In the case where the warm water in circulation has reached a temperature preset by the controller 150, the circulating pump 107 stops. Based on that the circulating pump 107 has stopped, the warm water gradually ceases to circulate in the hot water supply device 100.

During the instant hot water circulation mode, the circulating pump 107 sometimes has an ON failure and ceases to accept control from the controller 150. When the circulating pump 107 changes to the ON failure state, even though the temperature of the warm water in circulation has reached the temperature preset by the controller 150, the warm water continues to circulate because the circulating pump 107 does not stop.

The controller 150 stores a state of an operation mode (such as the hot water supply mode and the instant hot water circulation mode) of the hot water supply device 100 in an internal memory, and acquires a detection result of the amount of water in the path 170 from the flow detector 108. Hence, based on that the amount of water flowing through the path 170 is equal to or larger than a predetermined threshold value while the operation mode of the hot water supply device 100 is not the instant hot water circulation mode, the controller 150 may determine that the circulating pump 107 has an ON failure. The controller 150 is able to notify the user of the ON failure of the circulating pump 107 by an alarm or the like. As described above, the hot water supply device 100 with a circulation port is able to detect the ON failure of the circulating pump 107 in the instant hot water circulation mode.

FIG. 2 illustrates one example of the hot water supply device 200 without a circulation port. The hot water supply device 200 includes a bypass servo 201, a flow detector 202, temperature detectors 203 and 205, a heat exchanger 204, a water servo 206, a circulating pump 207, ports 211 and 213, and a controller 250.

The bypass servo 201, the flow detector 202, the temperature detectors 203 and 205, the heat exchanger 204, the water servo 206, the circulating pump 207, the ports 211 and 213 and the controller 250 of the hot water supply device 200 respectively correspond to the bypass servo 101, the flow detector 102, the temperature detectors 103 and 105, the heat exchanger 104, the water servo 106, the circulating pump 107, the ports 111 and 113 and the controller 150 of the hot water supply device 100. In addition, paths 255, 260 and 265 respectively correspond to the paths 155, 160 and 165.

As compared with the hot water supply device 100, it is clear that the hot water supply device 200 includes neither a circulation port nor a path corresponding to the path 170. Instead, the hot water supply device 200 includes the circulating pump 207 on the upstream side of the bypass servo 201. The difference in configuration between the hot water supply devices 100 and 200 is due to a difference in configuration of water supply facilities between countries or regions.

As shown in FIG. 2, in a water supply facility in a certain country or region, a path 280 through which water flowing in from the water pipe 110 flows and a path 281 through which warm water flowing out of the hot water supply device 200 flows are connected to each other via a path 282. A valve 214 for backflow prevention is provided in the path 282. The valve 214 is a valve for preventing inflow of water from the path 280 to the path 281.

In the water supply facility of this configuration, it is assumed that warm water is circulated in the hot water supply device 200 via the port 211 and the port 213. Hence, the hot water supply device 200 does not include a circulation port connected to a path branched from the path 281. In addition, since it is necessary to circulate the warm water through the paths 281 and 260, the hot water supply device 200 includes the circulating pump 207 on the downstream side of the port 211.

Next, an outline of operations in the hot water supply mode and the instant hot water circulation mode in the hot water supply device 200 will be described. In addition, a problem of the hot water supply device 200 in the case where the circulating pump 207 has an ON failure during the instant hot water circulation mode will also be described.

In the hot water supply mode, the hot water supply device 200 heats the water flowing in from the water pipe 110 with the heat exchanger 204, and causes warm water to flow out from the port 213. In the case where the valve 120 is open, the warm water flowing out from the port 213 flows out from the hot water faucet 140. In the case where the warm water flowing through the path 281 flows out from the hot water faucet 140, since no water pressure is applied to the valve 214, the warm water does not flow into the path 280 from the path 281, or only a small amount of the warm water flows into the path 280 from the path 281.

In the instant hot water circulation mode, the hot water supply device 200 heats the water flowing in from the water pipe 110 with the heat exchanger 204, and causes warm water to flow out from the port 213. The circulating pump 207 is operating during the instant hot water circulation mode, and flows warm water in a direction from the port 211 to the path 255. As long as the valve 120 is closed, the warm water that has flowed out from the port 213 is subjected to a force of flowing the warm water into the port 211 by the circulating pump 207. Hence, the warm water that has flowed out from the port 213 flows into the port 211 via the paths 281, 282 and 280. As a result, the warm water circulates through the path 280, the path 255, the heat exchanger 204, the path 265, the path 281 and the path 282.

In the case where the temperature of the warm water in circulation has reached a temperature preset by the controller 250, the circulating pump 207 stops. Based on that the circulating pump 207 has stopped, the warm water gradually ceases to circulate in the hot water supply device 200.

When the circulating pump 207 changes to the ON failure state, even though the temperature of the warm water in circulation has reached the temperature preset by the controller 250, the warm water continues to circulate because the circulating pump 207 does not stop.

While the hot water supply device 100 is able to detect the ON failure of the circulating pump 107, the hot water supply device 200 is unable to clearly detect the ON failure of the circulating pump 207 due to the configuration of the device. A reason why the hot water supply device 200 is unable to detect the ON failure of the circulating pump 207 is that the path before and after the circulating pump 207 serves as both an inflow path during the hot water supply mode and a circulation path during the instant hot water circulation mode.

As shown in FIG. 2, the controller 250 needs to use a detection result of the flow detector 202 to determine whether the circulating pump 207 has failed. In the case where the flow detector 202 does not detect a flow of water or warm water after completion of the instant hot water circulation mode, the controller 250 is able to determine that the circulating pump 207 has stopped normally. However, in contrast, in the case where the flow detector 202 detects a flow of water or warm water after completion of the instant hot water circulation mode, the controller 250 is unable to determine whether the circulating pump 207 has an ON failure. The reason is as follows. Even if the circulating pump 207 has been turned off normally, in the case where the user opens the valve 120 and causes warm water to flow out from the hot water faucet 140 during the hot water supply mode, since water flows from the water pipe 110 into the hot water supply device 200, the flow detector 202 may detect the flow of water or warm water. In this way, the hot water supply device 200 without a circulation port is unable to clearly determine whether an ON failure of the circulating pump 207 has occurred or the user is just using warm water only by the detection result of the flow detector 202.

If the hot water supply device 200 is circulating warm water at a set high temperature during the instant hot water circulation mode, when the circulating pump 207 has an ON failure, the high-temperature warm water continues to circulate via the path 280 even after completion of the instant hot water circulation mode. In this state, when the user opens the valve 130, the high-temperature warm water flows out from the hot water faucet 140, which is dangerous. Hence, in order to avoid such a situation, the hot water supply device 200 ensures the safety of the user by a control method to be described later.

[Configuration of Controller]

FIG. 3 illustrates one example of a configuration of the controller 250. The controller 250 includes a central processing unit (CPU) 301, a memory 302, an electronic circuit 303, an interface 304, and a bus 305. The controller 250 communicates with various sensors and actuators of the hot water supply device 200, and controls the hot water supply device 200. In addition, the controller 250 notifies the user of information about the hot water supply device 200 by a notification device 306. Further, the controller 250 may control the hot water supply device 200 based on the user's input accepted by a remote controller 307.

The CPU 301 executes various programs read in the memory 302 or refers to data. In one aspect, the CPU 301 may be a built-in CPU, or a field-programmable gate array (FPGA), or may be composed of a combination of the above. The CPU 301 may execute a program for realizing various functions of the hot water supply device 200. As one example, the CPU 301 may include ON/OFF operations of an operation switch of the hot water supply device 200, setting of a hot water supply temperature and various time settings (also referred to as “timer settings”), and the like. In addition, based on these settings, the CPU 301 controls a motor or a combustion mechanism or the like in the hot water supply device 200.

The memory 302 stores the programs executed by the CPU 301 and the data referred to by the CPU 301. In one aspect, a dynamic random access memory (DRAM) or static random access memory (SRAM) may be used as the memory 302.

The electronic circuit 303 is a circuit having a dedicated function. The electronic circuit 303 may perform a specific processing such as data conversion or actuator control on behalf of the CPU 301. In one aspect, the electronic circuit 303 may be composed of at least one application specific integrated circuit (ASIC), at least one FPGA, or a combination thereof.

The interface 304 inputs and outputs signals to and from an external machine. The CPU 301 may control other devices via the interface 304. The interface 304 may be connected to at least a combustion mechanism 310 of the heat exchanger 204, the circulating pump 207, the temperature detectors 203 and 205, the flow detector 202, the bypass servo 201, and the water servo 206. Further, the interface 304 may be connected to the notification device 306 and the remote controller 307.

In one aspect, the interface 304 may be composed of a wired interface, a wireless interface, or a combination thereof, inputting and outputting or transmitting and receiving signals of arbitrary form. In another aspect, the interface 304 may transmit and receive data to and from the notification device 306, the remote controller 307 and any other device, using a communication protocol such as the Transmission Control Protocol/Internet Protocol (TCP/IP) and the User Datagram Protocol (UDP). In addition, the interface 304 may communicate with a cloud service or the like. The bus 305 is mutually connected to the CPU 301, the memory 302, the electronic circuit 303 and the interface 304.

The notification device 306 may be composed of at least one speaker, at least one display, a communication device with respect to at least one other device, or a combination thereof. As one example, the notification device 306 may notify acceptance of various settings in the remote controller 307 or completion of an operation (such as boiling water) whose reservation has been accepted. In addition, in the case where an abnormality occurs in the hot water supply device 200, the notification device 306 may also notify the occurrence of the abnormality.

The remote controller 307 is a controller prepared separately from a main body of the hot water supply device 200, accepts input of various operations from the user, and outputs the accepted input to the controller 250. In one aspect, the remote controller 307 may be integrated with the hot water supply device 200. The operations of the hot water supply device 200 hereinafter described with reference to FIG. 4 to FIG. 8 may be realized by controlling the hot water supply device 200 by the controller 250 shown in FIG. 3. The operations shown in FIG. 4 to FIG. 8 ensure the safety of the user when the circulating pump 207 of the hot water supply device 200 described in FIG. 2 has an ON failure.

[Outline of Operation of Hot Water Supply Device 200 in Hot Water Supply Mode]

FIG. 4 illustrates one example of an outline of an operation of the hot water supply device 200 in the hot water supply mode. Referring to FIG. 4, a description is given of how the CPU 301 controls the hot water supply device 200 based on the temperature settings and operation mode settings input to and accepted by the remote controller 307.

First of all, a description is given of an operation of the hot water supply device 200 in the hot water supply mode. The hot water supply mode is generally a mode in which the user uses the warm water flowing out from the hot water faucet 140. In the case where the hot water supply device 200 is operating in the hot water supply mode, the warm water heated in the heat exchanger 204 flows out from the hot water faucet 140 when the valve 120 is open. While the warm water heated in the hot water supply device 200 is being used, water is supplied at all times from the water pipe 110 to the hot water supply device 200. An arrow 400 in FIG. 4 represents a flow of water and warm water during the hot water supply mode.

Next described is an operation of the CPU 301 when the remote controller 307 accepts a temperature setting operation in the case where the hot water supply device 200 is operating in the hot water supply mode. In the case where the hot water supply device 200 is operating in the hot water supply mode, when the remote controller 307 accepts input of setting of a high temperature (for example, up to 70° C.), the CPU 301 controls the heat exchanger 204 so that the temperature of the warm water flowing out of the hot water supply device 200 becomes equal to the temperature as set in the accepted settings.

The hot water supply mode is a mode on the premise that warm water is used, and it is assumed that the user understands that high-temperature warm water flows out from the hot water faucet 140. In addition, as indicated by the arrow 400, the warm water flowing out from the port 213 does not flow into the port 211 if the valve 120 is open. Therefore, since it is conceivable that the user is less likely to get burned, the CPU 301 controls the hot water supply device 200 so that the temperature of the warm water becomes equal to that as set in the accepted temperature settings.

Next described is an operation of the CPU 301 when the remote controller 307 accepts an input operation of the instant hot water circulation mode in the case where the hot water supply device 200 is operating in the hot water supply mode. The CPU 301 may perform two types of operations.

In a first operation, in the case where the input operation of the instant hot water circulation mode is accepted, the CPU 301 determines whether a currently set temperature of the warm water flowing out of the hot water supply device 200 is equal to or higher than a predetermined limit temperature (Th1). In the case where it is determined that the currently set temperature of the warm water flowing out of the hot water supply device 200 is equal to or higher than the predetermined limit temperature (Th1), the CPU 301 changes the set temperature to the limit temperature (Th1). In the case where it is determined that the currently set temperature of the warm water flowing out of the hot water supply device 200 is lower than the predetermined limit temperature (Th1), the CPU 301 does not change the temperature settings. Next, the CPU 301 causes the hot water supply device 200 to transition into the instant hot water circulation mode in a state in which the set temperature is equal to or lower than the limit temperature (Th1).

The limit temperature (Th1) here is, for example, about 48° C. 48° C. is one example, and examples of the limit temperature (Th1) are not limited thereto. The limit temperature (Th1) may be a temperature at which the user will not get burned when using the warm water flowing out from the hot water faucet 140.

Since the hot water supply device 200 operates based on the above first operation, if the circulating pump 207 has an ON failure, even if the user opens the valve 130 (in the expectation that water will be supplied) and warm water flows out from the hot water faucet 140, the temperature of the warm water is equal to or lower than the limit temperature (Th1), and the user will not get burned.

In one aspect, in a state in which the flow detector 202 has detected no flow of warm water after completion of the instant hot water circulation mode (in a state in which the circulating pump 207 is confirmed to have stopped), the CPU 301 may return the set temperature to the original one.

In a second operation, in the case where the input operation of the instant hot water circulation mode is accepted, the CPU 301 determines whether the currently set temperature of the warm water flowing out of the hot water supply device 200 is equal to or higher than the predetermined limit temperature (Th1).

In the case where it is determined that the currently set temperature of the warm water flowing out of the hot water supply device 200 exceeds the predetermined limit temperature (Th1), the CPU 301 prevents the hot water supply device 200 from transitioning into the instant hot water circulation mode. In the case where it is determined that the currently set temperature of the warm water flowing out of the hot water supply device 200 is equal to or lower than the predetermined limit temperature (Th1), the CPU 301 causes the hot water supply device 200 to transition into the instant hot water circulation mode. In one aspect, in the case where the CPU 301 prevents the hot water supply device 200 from transitioning into the instant hot water circulation mode, the notification device 306 may notify the user that the hot water supply device 200 is unable to transition into the instant hot water circulation mode.

Since the hot water supply device 200 operates based on the above second operation, the hot water supply device 200 does not transition into the instant hot water circulation mode at the set temperature exceeding the limit temperature (Th1). Hence, even if the hot water supply device 200 is in the instant hot water circulation mode and the circulating pump 207 has an ON failure, the user will not get burned.

[Outline of Operation of Hot Water Supply Device 200 in Instant Hot Water Circulation Mode]

FIG. 5 illustrates one example of an outline of an operation of the hot water supply device 200 in the instant hot water circulation mode. Referring to FIG. 5, a description is given of an operation at the completion of the instant hot water circulation mode in the first operation described in FIG. 4.

First of all, a description is given of an operation of the hot water supply device 200 in the instant hot water circulation mode. The circulating pump 207 is operating during the instant hot water circulation mode. In addition, generally, the user does not use the hot water faucet 140 and the valve 120 is closed. Hence, warm water circulates in the hot water supply device 200 along a flow indicated by an arrow 500.

Next described is an operation of the hot water supply device 200 at the completion of the instant hot water circulation mode. Based on that the temperature of the warm water in circulation has reached the set temperature, the CPU 301 causes the hot water supply device 200 to complete the instant hot water circulation mode. Based on a detection result of the temperature detector 203 or 205, the CPU 301 may determine whether the temperature of the warm water in circulation has reached the set temperature.

The CPU 301 causes the hot water supply device 200 to complete the instant hot water circulation mode based on the following procedure. As a first step, the CPU 301 changes the operation mode of the hot water supply device 200 stored in the memory 302 from the instant hot water circulation mode to another mode (such as a standby mode). As a second step, the CPU 301 stops the circulating pump 207. As a third step, the CPU 301 regularly refers to a detection value of the flow detector 202 in a predetermined period until a flow of warm water detected by the flow detector 202 becomes equal to or lower than a predetermined threshold value. As a fourth step, based on that the flow of the warm water detected by the flow detector 202 has become equal to or less than the predetermined threshold value in the predetermined period (based on the determination that the flow of the arrow 500 has stopped), the CPU 301 determines that the circulating pump 207 has stopped. As a fifth step, in the case where the set temperature input by the user is equal to or higher than the limit temperature (Th1), the CPU 301 returns the set temperature to the original one (returns the currently set temperature to the set temperature input by the user).

FIG. 6 illustrates one example of an outline of an operation of the hot water supply device 200 in the case where the circulating pump 207 has an ON failure in the instant hot water circulation mode. Referring to FIG. 6, a description is given of an operation at the completion of the instant hot water circulation mode in the first operation described in FIG. 4 in the case where the circulating pump 207 has an ON failure.

The description of the first to third steps is the same as that of FIG. 5. In the fourth step, in the case where the circulating pump 207 has an ON failure, since the circulating pump 207 continues to operate, the flow of the warm water detected by the flow detector 202 during the predetermined period will not become equal to or lower than the predetermined threshold value. If the circulating pump 207 has an ON failure, when the user opens the valve 120, warm water flows out from the hot water faucet 140 as indicated by an arrow 600. In the case where the warm water continues to flow even after a certain period like this, the CPU 301 determines that the circulating pump 207 has an ON failure. As the fifth step, the CPU 301 causes the notification device 306 to notify a message that the circulating pump 207 has an ON failure. By referring to the content notified from the notification device 306, the user is able to notice an abnormality in the hot water supply device 200 and able to contact a service person or the like.

[Operation Procedure of Hot Water Supply Device 200]

FIG. 7 illustrates an example of the first operation in the hot water supply device 200 in the instant hot water circulation mode. The processing shown in FIG. 7 is a flow of processing by the CPU 301 when realizing the first operation described in FIG. 4 to FIG. 6. In one aspect, the CPU 301 may read from the memory 302 a program for performing the processing of FIG. 7 and execute the program. In another aspect, a part or all of the processing may be realized as a combination of circuit elements configured to execute the processing.

In step S705, when entering the instant hot water circulation mode, the CPU 301 sets a set temperature of hot water supply to be equal to or lower than a limit temperature (Th1). In the case where an original set temperature (T) exceeds the limit temperature (Th1), the CPU 301 changes the set temperature from the original set temperature (T) to the limit temperature (Th1). Otherwise, the CPU 301 maintains the set temperature at the original set temperature (T). In the case where the set temperature is changed to the limit temperature (Th1), the CPU 301 stores information of the original set temperature (T) in the memory 302 for the processing of step S745.

In step S710, the CPU 301 outputs an ON command to the circulating pump 207. When the ON command is input from the CPU 301, the circulating pump 207 operates and circulates warm water. In one aspect, the ON command may be a digital signal or an analog signal. In another aspect, the CPU 301 may output the ON command to the electronic circuit 303, and the electronic circuit 303 to which the ON command has been input may directly control the circulating pump 207.

In step S715, in the case where it is determined that a temperature of the warm water in circulation has reached the set temperature based on a detection result of the temperature detectors 203 and 205, the CPU 301 changes the state of the hot water supply device 200 to a state of completion of instant hot water circulation. In the case where the CPU 301 has set the set temperature to be equal to the limit temperature (Th1) in step S705, the CPU 301 changes the state of the hot water supply device 200 to the state of completion of instant hot water circulation based on that the temperature of the warm water in circulation has reached the limit temperature (Th1).

In one aspect, the CPU 301 may store the state (such as hot water supply standby, in hot water supply, instant hot water standby, in instant hot water circulation, and completion of instant hot water circulation) of the hot water supply device 200 in the memory 302. In that case, the CPU 301 manages the state of the hot water supply device 200 by rewriting the state of the hot water supply device 200 in the memory 302.

In step S720, the CPU 301 outputs an OFF command to the circulating pump 207. When the OFF command is input from the CPU 301, the circulating pump 207 stops. When the circulating pump 207 stops, the warm water in circulation ceases to circulate after a while. In one aspect, the OFF command may be a digital signal or an analog signal. In another aspect, the CPU 301 may output the OFF command to the electronic circuit 303, and the electronic circuit 303 to which the OFF command has been input may stop the circulating pump 207.

In step S725, the CPU 301 determines whether a counter has a value equal to or less than an upper limit value (N). Based on the value of the counter, the CPU 301 determines whether a predetermined period (count number N) has elapsed from the start of counting. The value of the counter is used to determine whether the processing of step S735 has timed out. In the case where it is determined that the counter has a value equal to or lower than the upper limit value (N) (YES in step S725), the CPU 301 moves the control to step S730. Otherwise (NO in step S725), the CPU 301 moves the control to step S750.

In step S730, the CPU 301 counts up. In step S735, the CPU 301 determines whether the flow detector 202 has detected no water flow. That is, the CPU 301 determines whether the circulation of warm water has stopped. In the case where it is determined that the flow detector 202 has detected no water flow (YES in step S735), the CPU 301 moves the control to step S740. Otherwise (NO in step S735), the CPU 301 moves the control to step S725.

In step S740, the CPU 301 determines that the circulating pump 207 has stopped normally, and removes the limit on the set temperature. In the case where the CPU 301 has changed the set temperature from the original set temperature (T) to the limit temperature (Th1) in step S705, the CPU 301 returns the set temperature to the original set temperature (T).

In step S745, the CPU 301 controls the heat exchanger 204 so that the warm water reaches the original set temperature (T). In step S750, the CPU 301 determines that the circulating pump 207 has not stopped normally, and outputs an alarm from the notification device 306.

FIG. 8 illustrates an example of the second operation in the hot water supply device 200. The processing shown in FIG. 8 is a flow of processing by the CPU 301 when realizing the second operation described in FIG. 4. In one aspect, the CPU 301 may read from the memory 302 a program for performing the processing of FIG. 8 and execute the program. In another aspect, a part or all of the processing may be realized as a combination of circuit elements configured to execute the processing.

In step S805, the CPU 301 sets the state of the hot water supply device 200 to a hot water supply standby mode. In step S810, the CPU 301 accepts an instant hot water ON command. In one aspect, the CPU 301 may accept the instant hot water ON command based on that an instant hot water switch of the remote controller 307 is pressed. In another aspect, the CPU 301 may accept the instant hot water ON command by pressing of a button or the like of the main body of the hot water supply device 200.

In step S815, when entering the instant hot water circulation mode, the CPU 301 determines whether the set temperature of hot water supply is equal to or lower than the limit temperature (Th1). In the case where it is determined that the set temperature of hot water supply is equal to or lower than the limit temperature (Th1) (YES in step S815), the CPU 301 moves the control to step S820. Otherwise (NO in step S815), the CPU 301 moves the control to step S810. In one aspect, when returning the control to step S810, the CPU 301 may notify the user from the notification device 306 that the instant hot water circulation mode cannot be entered.

In step S820, the CPU 301 sets the state of the hot water supply device 200 to an instant hot water standby mode. In step S825, the CPU 301 determines whether the hot water supply device 200 satisfies combustion start conditions. One example of the combustion start conditions includes whether the current temperature of the warm water is lower than the set temperature, whether the circulating pump 207 reacts, and the like. In the case where it is determined that the hot water supply device 200 satisfies the combustion start conditions (YES in step S825), the CPU 301 moves the control to step S830. Otherwise (NO in step S825), the CPU 301 moves the control to step S820. In one aspect, when returning the control to step S820, the CPU 301 may notify the user from the notification device 306 that the hot water supply device 200 does not satisfy the combustion start conditions.

In step S830, the CPU 301 outputs the ON command to the circulating pump 207. When the ON command is input from the CPU 301, the circulating pump 207 operates and circulates the warm water.

In step S835, the CPU 301 sets an upper limit of the set temperature of hot water supply to be equal to or lower than the limit temperature (Th1) after the start of the instant hot water circulation. That is, in the case where the hot water supply device 200 is operating in the instant hot water circulation mode, the CPU 301 does not accept input of a temperature set higher than the limit temperature (Th1).

In step S840, the CPU 301 sets the state of the hot water supply device 200 to the state of completion of instant hot water circulation based on that the temperature of the warm water in circulation has reached the set temperature. In step S845, the CPU 301 outputs the OFF command to the circulating pump 207. When the OFF command is input from the CPU 301, the circulating pump 207 stops. In step S850, the CPU 301 removes the upper limit on the set temperature of hot water supply set in step S835. After the removal of the upper limit on the set temperature, the CPU 301 may accept input of a temperature set higher than the limit temperature (Th1).

[Other Device Configuration]

FIG. 9 illustrates another example of a hot water supply device without a circulation port. As compared with the hot water supply device 200, a hot water supply device 900 includes a path that bypasses the upstream and downstream of the circulating pump 207, a flow detector 901 provided in the path, and a valve 902 for backflow prevention.

Since the hot water supply device 900 includes the flow detector 901, in the case where the flow detector 202 detects a flow of water or warm water after completion of the instant hot water circulation mode, the controller 250 is able to determine whether the circulating pump 207 has an ON failure, or whether the user opens the valve 120 and causes warm water to flow out from the hot water faucet 140.

Specifically, in the case where the controller 250 has turned off the circulating pump 207, when the flow detector 202 detects a water flow and the flow detector 901 detects no water flow, the controller 250 is able to determine that the circulating pump 207 has an ON failure. The reason is as follows. During operation of the circulating pump 207, since water or warm water is sucked into the circulating pump 207, the water or warm water preferentially flows into the circulating pump 207 than into the flow detector 901. As a result, the flow detector 901 detects almost no water flow.

In contrast, in the case where the controller 250 has turned off the circulating pump 207, when both the flow detector 202 and the flow detector 901 detect a water flow, the controller 250 is able to determine that the circulating pump 207 has no ON failure (the user opens the valve 120 and causes warm water to flow out from the hot water faucet 140). The reason is as follows. In the case where the circulating pump 207 has stopped and the user opens the valve 120 and causes warm water to flow out from the hot water faucet 140, the water or warm water does not preferentially flow into the circulating pump 207. As a result, the water or warm water also flows into the flow detector 901.

As described above, the hot water supply device 200 according to the present embodiment heats warm water within a range of equal to or lower than the predetermined limit temperature in the instant hot water circulation mode. Alternatively, in the case where the set temperature of hot water supply exceeds the predetermined limit temperature, the hot water supply device 200 does not transition into the instant hot water circulation mode. By this control, the temperature of the warm water in the instant hot water circulation mode and at the completion of the instant hot water circulation mode is limited to a temperature at which the user does not get burned. Hence, even if the user opens the valve 130 when the circulating pump 207 has an ON failure, the user will not get burned.

The techniques disclosed as above may be summarized as follows.

(Configuration 1) A hot water supply device according to one embodiment includes: a first pipe connected to a water inlet; a flow detector detecting a flow of water in the first pipe; a heating mechanism heating the water flowing in from the first pipe; and a second pipe through which warm water heated by the heating mechanism flows. The second pipe is connected to the first pipe via an external third pipe. The hot water supply device further includes: a circulating pump disposed in a path of the first pipe, sending the warm water in the third pipe toward the heating mechanism during operation; and a control device controlling the circulating pump and the heating mechanism. Based on acceptance of an execution command of an instant hot water circulation mode, the control device operates the circulating pump, and, in response to a set hot water output temperature exceeding a predetermined limit temperature, adjusts a heating temperature of the heating mechanism, so that the temperature of the warm water in the instant hot water circulation mode becomes equal to or lower than the limit temperature.

(Configuration 2) A hot water supply device according to another embodiment includes: a first pipe connected to a water inlet; a flow detector detecting a flow of water in the first pipe; a heating mechanism heating the water flowing in from the first pipe; and a second pipe through which warm water heated by the heating mechanism flows. The second pipe is connected to the first pipe via an external third pipe. The hot water supply device further includes: a circulating pump disposed in a path of the first pipe, sending the warm water in the third pipe toward the heating mechanism during operation; and a control device controlling the circulating pump and the heating mechanism. The control device determines whether a set hot water output temperature is equal to or lower than a predetermined limit temperature based on acceptance of an execution command of an instant hot water circulation mode, and operates the hot water supply device in the instant hot water circulation mode based on that the set hot water output temperature is equal to or lower than the limit temperature.

(Configuration 3) The hot water supply device according to one aspect further includes, in addition to Configuration 2, a notification device that notifies a user of information. The notification device notifies the user that there is no transition into the instant hot water circulation mode based on that the set hot water output temperature exceeds the limit temperature.

(Configuration 4) A hot water supply device according to still another embodiment includes: a first pipe connected to a water inlet; a flow detector detecting a flow of water in the first pipe; a heating mechanism heating the water flowing in from the first pipe; and a second pipe through which warm water heated by the heating mechanism flows. The second pipe is connected to the first pipe via an external third pipe. The hot water supply device further includes: a circulating pump disposed in a path of the first pipe, sending the warm water in the third pipe toward the heating mechanism during operation; and a control device controlling the circulating pump and the heating mechanism. Based on that the hot water supply device is operating in the instant hot water circulation mode, the control device sets a limit on a heating temperature of the heating mechanism so that a temperature of the warm water in circulation becomes equal to or lower than a predetermined limit temperature. Stop the circulating pump and end the instant hot water heater circulation mode. Based on that the flow detected by the flow detector is less than a first flow after the end of the instant hot water circulation mode, the control device determines that the circulation of the warm water has ended. Based on the determination that the circulation of the warm water has ended, the control device removes the limit on the heating temperature of the heating mechanism.

(Configuration 5) The hot water supply device according to one aspect further includes, in addition to Configuration 4, a memory storing the settings of the hot water supply device. The control device accepts input of the set hot water output temperature from a remote controller, and stores the input set hot water output temperature in the memory. The removal of the limit on the heating temperature of the heating mechanism includes the following. In the case where the input of the temperature set to exceed the limit temperature is accepted, after completion of the instant hot water circulation mode, the heating temperature of the heating mechanism is raised based on the set hot water output temperature read from the memory.

(Configuration 6) The hot water supply device according to one aspect further includes, in addition to Configuration 4, a notification device notifying a user of information. Based on that the flow detected by the flow detector does not become less than the first flow even after a predetermined time has elapsed from the end of the instant hot water circulation mode, the notification device notifies a failure that the circulating pump does not stop, that is, a failure of the hot water supply device.

(Configuration 7) The hot water supply device according to one aspect further includes, in addition to Configuration 4, a fourth pipe bypassing the upstream side of the circulating pump in the first pipe and the downstream side of the circulating pump, and another flow detector disposed in a path of the fourth pipe. In the case where the instant hot water circulation mode is ended and the flow detected by the flow detector is equal to or higher than the first flow, based on that a flow detected by the another flow detector is less than a second flow, the control device detects a failure of the circulating pump.

(Configuration 8) In the hot water supply device according to one aspect, in addition to any of Configurations 1 to 7, the limit temperature is a maximum set temperature of warm water in the instant hot water circulation mode.

(Configuration 9) In the hot water supply device according to one aspect, in addition to any of Configurations 1 to 8, a valve is disposed in a path of the third pipe. The valve limits a flow of the warm water in the third pipe in a direction from the second pipe to the first pipe.

(Configuration 10) The hot water supply device according to one aspect further includes, in addition to any of Configurations 1 to 9, a fifth pipe connecting the downstream side of the circulating pump in the first pipe to the second pipe, and a flow adjustment device adjusting the amount of water flowing from the first pipe into the second pipe via the fifth pipe.

The embodiments disclosed herein are examples in all aspects and should not be interpreted as limitations. The scope of the disclosure is defined by claims instead of the above description, and it is intended to include all modifications within the scope of the claims and the equivalents thereof. In addition, the disclosure described in the embodiments and modifications is intended to be implemented alone or in combination whenever possible. 

What is claimed is:
 1. A hot water supply device, comprising: a first pipe connected to a water inlet; a flow detector detecting a flow of water in the first pipe; a heating mechanism heating the water flowing in from the first pipe; a second pipe through which warm water heated by the heating mechanism flows, the second pipe being connected to the first pipe via an external third pipe; a circulating pump disposed in a path of the first pipe, sending the warm water in the third pipe toward the heating mechanism during operation; and a control device controlling the circulating pump and the heating mechanism, wherein the control device is configured to operate the circulating pump based on acceptance of an execution command of an instant hot water circulation mode, and in response to a set hot water output temperature exceeding a predetermined limit temperature, adjust a heating temperature of the heating mechanism, so that a temperature of the warm water in the instant hot water circulation mode becomes equal to or lower than the limit temperature.
 2. A hot water supply device, comprising: a first pipe connected to a water inlet; a flow detector detecting a flow of water in the first pipe; a heating mechanism heating the water flowing in from the first pipe; a second pipe through which warm water heated by the heating mechanism flows, the second pipe being connected to the first pipe via an external third pipe; a circulating pump disposed in a path of the first pipe, sending the warm water in the third pipe toward the heating mechanism during operation; and a control device controlling the circulating pump and the heating mechanism, wherein the control device is configured to determine whether a set hot water output temperature is equal to or lower than a predetermined limit temperature based on acceptance of an execution command of an instant hot water circulation mode, and operate the hot water supply device in the instant hot water circulation mode based on that the set hot water output temperature is equal to or lower than the limit temperature.
 3. A hot water supply device, comprising: a first pipe connected to a water inlet; a flow detector detecting a flow of water in the first pipe; a heating mechanism heating the water flowing in from the first pipe; a second pipe through which warm water heated by the heating mechanism flows, the second pipe being connected to the first pipe via an external third pipe; a circulating pump disposed in a path of the first pipe, sending the warm water in the third pipe toward the heating mechanism during operation; and a control device controlling the circulating pump and the heating mechanism, wherein the control device is configured to based on that the hot water supply device is operating in an instant hot water circulation mode, set a limit on a heating temperature of the heating mechanism so that a temperature of the warm water in circulation becomes equal to or lower than a predetermined limit temperature, stop the circulating pump and end the instant hot water circulation mode, based on that the flow detected by the flow detector is less than a first flow after the end of the instant hot water circulation mode, determine that the circulation of the warm water has ended, and based on the determination that the circulation of the warm water has ended, remove the limit on the heating temperature of the heating mechanism. 